1. Field of the Invention
The present invention relates to gas turbine blades having internal cooling structures.
2. Description of the Related Art
In recent years, the working gases of gas turbines are increasingly getting higher in temperature for better thermal efficiency. This requires at the same time improvements in the cooling performance of gas turbine blades. A gas turbine blade having internal cooling structures allows cooling air to flow through the interior of the blade, and the blade is cooled by heat exchange with the cooling air. At the trailing edge of the blade, however, a sufficient air channel height often cannot be secured. Thus, pin fin cooling is usually employed in the trailing-edge cooling channel, whereby pin fins are disposed between a suction-side cooling target surface and a pressure-side cooling target surface (i.e., between the inner wall surfaces of the blade). Such pin fins are also effective in increasing the strength of the blade against stress and vibration.
However, the suction-side and pressure-side blade surfaces of the gas turbine blade are subject to different thermal loads. As the temperature difference between the pressure and suction sides of the trailing edge increases with increases in combustion temperature, the trailing edge may be exposed to excessive thermal stresses accordingly. Thus, to make those temperatures equal, the cooling performance of either the pressure side or the suction side needs to be enhanced, but typical pin fins have a symmetrical shape. This means that the heat transfer rate of the suction-side and the heat transfer rate of the pressure-side are substantially the same.
JP-2009-041433-A discloses a method for enhancing the suction-side or pressure-side cooling performance of pin fin structures. In the method, triangular-pyramid-shaped vortex generators are additionally disposed only on the cooling target surface for which cooling performance needs to be enhanced. The vortex generators produce vertical vortices, thereby enhancing cooling of that cooling target surface.